export default function loginBgAnimation() {
  const windowWidth =
    document.documentElement.clientWidth || document.body.clientWidth;
  const windowHeight =
    document.documentElement.clientHeight || document.body.clientHeight;
  let count = 0;
  const canvas = document.getElementById("bg-canvas") as HTMLCanvasElement,
    ctx = canvas.getContext("2d") as CanvasRenderingContext2D,
    w = (canvas.width = windowWidth),
    h = (canvas.height = windowHeight),
    hue = 217,
    stars: IntStart[] = [],
    maxStars = 1500; //星星数量

  const canvas2 = document.createElement("canvas"),
    ctx2 = canvas2.getContext("2d") as CanvasRenderingContext2D;
  canvas2.width = 100;
  canvas2.height = 100;
  const half = canvas2.width / 2,
    gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);
  gradient2.addColorStop(0.025, "#CCC");
  gradient2.addColorStop(0.1, "hsl(" + hue + ", 61%, 33%)");
  gradient2.addColorStop(0.25, "hsl(" + hue + ", 64%, 6%)");
  gradient2.addColorStop(1, "transparent");

  ctx2.fillStyle = gradient2;
  ctx2.beginPath();
  ctx2.arc(half, half, half, 0, Math.PI * 2);
  ctx2.fill();

  // End cache

  function random(min: number, max = 0) {
    if (arguments.length < 2) {
      max = min;
      min = 0;
    }

    if (min > max) {
      const hold = max;
      max = min;
      min = hold;
    }

    return Math.floor(Math.random() * (max - min + 1)) + min;
  }

  function maxOrbit(x: number, y: number) {
    const max = Math.max(x, y),
      diameter = Math.round(Math.sqrt(max * max + max * max));
    return diameter / 2;
    //星星移动范围，值越大范围越小，
  }
  interface IntStart {
    orbitRadius: number;
    radius: number;
    orbitX: number;
    orbitY: number;
    timePassed: number;
    speed: number;
    alpha: number;
    draw: () => void;
  }
  const Star = function (this: IntStart) {
    this.orbitRadius = random(maxOrbit(w, h));
    this.radius = random(60, this.orbitRadius) / 18;
    //星星大小
    this.orbitX = w / 2;
    this.orbitY = h / 2;
    this.timePassed = random(0, maxStars);
    this.speed = random(this.orbitRadius) / 500000;
    //星星移动速度
    this.alpha = random(2, 10) / 10;

    count++;
    stars[count] = this;
  };

  Star.prototype.draw = function () {
    const x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX,
      y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY,
      twinkle = random(10);

    if (twinkle === 1 && this.alpha > 0) {
      this.alpha -= 0.05;
    } else if (twinkle === 2 && this.alpha < 1) {
      this.alpha += 0.05;
    }

    ctx.globalAlpha = this.alpha;
    ctx.drawImage(
      canvas2,
      x - this.radius / 2,
      y - this.radius / 2,
      this.radius,
      this.radius,
    );
    this.timePassed += this.speed;
  };

  for (let i = 0; i < maxStars; i++) {
    new Star.prototype.constructor();
  }

  function animation() {
    ctx.globalCompositeOperation = "source-over";
    ctx.globalAlpha = 0.5; //尾巴
    ctx.fillStyle = "hsla(" + hue + ", 64%, 6%, 2)";
    ctx.fillRect(0, 0, w, h);

    ctx.globalCompositeOperation = "lighter";
    for (let i = 1, l = stars.length; i < l; i++) {
      stars[i].draw();
    }

    window.requestAnimationFrame(animation);
  }

  animation();
}
